From 5c401308017f256ae9de804b4a1c65be1d390571 Mon Sep 17 00:00:00 2001 From: Christoffer Dall Date: Mon, 28 Oct 2019 14:05:41 +0100 Subject: KVM: arm64: Don't set HCR_EL2.TVM when S2FWB is supported On CPUs that support S2FWB (Armv8.4+), KVM configures the stage 2 page tables to override the memory attributes of memory accesses, regardless of the stage 1 page table configurations, and also when the stage 1 MMU is turned off. This results in all memory accesses to RAM being cacheable, including during early boot of the guest. On CPUs without this feature, memory accesses were non-cacheable during boot until the guest turned on the stage 1 MMU, and we had to detect when the guest turned on the MMU, such that we could invalidate all cache entries and ensure a consistent view of memory with the MMU turned on. When the guest turned on the caches, we would call stage2_flush_vm() from kvm_toggle_cache(). However, stage2_flush_vm() walks all the stage 2 tables, and calls __kvm_flush-dcache_pte, which on a system with S2FWB does ... absolutely nothing. We can avoid that whole song and dance, and simply not set TVM when creating a VM on a system that has S2FWB. Signed-off-by: Christoffer Dall Signed-off-by: Marc Zyngier Reviewed-by: Mark Rutland Link: https://lore.kernel.org/r/20191028130541.30536-1-christoffer.dall@arm.com --- arch/arm64/include/asm/kvm_emulate.h | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) (limited to 'arch/arm64/include/asm/kvm_emulate.h') diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h index d69c1efc63e7..6e92f6c7b1e4 100644 --- a/arch/arm64/include/asm/kvm_emulate.h +++ b/arch/arm64/include/asm/kvm_emulate.h @@ -53,8 +53,18 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu) /* trap error record accesses */ vcpu->arch.hcr_el2 |= HCR_TERR; } - if (cpus_have_const_cap(ARM64_HAS_STAGE2_FWB)) + + if (cpus_have_const_cap(ARM64_HAS_STAGE2_FWB)) { vcpu->arch.hcr_el2 |= HCR_FWB; + } else { + /* + * For non-FWB CPUs, we trap VM ops (HCR_EL2.TVM) until M+C + * get set in SCTLR_EL1 such that we can detect when the guest + * MMU gets turned on and do the necessary cache maintenance + * then. + */ + vcpu->arch.hcr_el2 |= HCR_TVM; + } if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) vcpu->arch.hcr_el2 &= ~HCR_RW; -- cgit v1.2.3-59-g8ed1b